There are known several systems for electrostatically printing on receiving medias. One system is called xerographic or xerography which involves placing a uniform charge on a photoconductive element, selectively exposing this charge to light in image configuration to form a latent image, applying a marking material to the latent image and subsequently transferring the developed image to a receiving sheet such as bond paper or the like, and the image fixed by heat or pressure. This basic xerographic process is disclosed in U.S. Pat. Nos. to Carlson 2,297,691; Middleton 2,663,636; Bixby 2,970,906; Schaffert 2,576,047 and Middleton and Reynolds 3,121,006. This xerographic process is limited to functional photoconductive materials that will hold a charge in the dark and have the ability to have charge dissipation upon exposure. Only a limited number of materials having desirable photoconductive properties have been found commercially acceptable such as selenium, zinc oxide, cadmium sulfate and a few other inorganic and organic materials.
Another electrostatic imaging system heretofore used is called electrography. In this process a dielectric material is charged in image configuration by various means such as print heads, electron beams, electronic stencils or shaped masks. While photoconductive insulators will only hold an electrical charge in the dark, dielectrics can hold an electrical charge in the presence of visible light which makes them more practical for various commercial uses such as in manufacturing processes. There are various patents and publications which specifically define the parameters of electrography such as Principles of Non-Impact Printing by Jerome S. Johnson, Palatino Press, 18792 Via Palatino, Irvine, Calif. 92715 and U.S. Pat. Nos. 5,025,273; 5,124,730; 5,126,769 and 5,162,179. As in xerography, the electrographic process also has some inherent drawbacks. One such drawback is that the dielectric surface layer must have a capacitance per unit area of at least 200 picofarad (PF) per cm squared and a resistivity of at least 10.sup.14 ohms centimeters bulk resistivity in order to properly function. A further disadvantage of prior art electrographic systems is that the dielectric paper structure used comprises a conducting layer having a resistivity of about 10.sup.7 ohms centimeters having coated thereon an insulating dielectric layer of about 10.sup.14 ohms centimeters resistivity. The manufacture of this dielectric paper is a relatively complex and expensive process. Thus, only dielectric materials of specific resistivities, coated over required specific conductive layers could heretofore be used in electrography.